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Zooplankton of Wellington Harbour, New Zealand

Plankton Sampling

Plankton Sampling

Plankton samples for analysis were obtained with a 36 gauge extra heavy grit gauze two foot diameter cone net, with a 2lb "Agee" preserving jar tied into the collar. The sampling gear was towed behind a launch using from 50 fathoms to 60 fathoms of 8lb three-quarter inch hemp. While taking a sample, the towing speed which varied between ¾ knot and 1½ knot was adjusted to correct for current, wave, and wind resistance to both the gear and the launch. This allowed the net to filter at depths between one fathom and three fathoms for the greater part of the ten to twenty minute towing period. By turning the launch in a tight circle once during each tow, the speed of the net in relation to the water was reduced allowing the net to sink and filter at depths of five or six fathoms for about five minutes.

On completion of every tow the plankton adhering to the mesh on the inside of the net was washed into the jar with rinses of sea water. The bulk of the sample was preserved in 5% formalin solution in the field, while a selected sub-sample was kept for the study of living material. The date, time of day, cloud and wind conditions, state of tide, and surface water temperature, were all recorded for each plankton tow.